If you've ever looked into the various programs available to download via bittorrent, you will probably have discovered µtorrent. Back then it was probably already tiny and full-featured at the same time. It even had customizations to better run inside WINE. But it didn't run natively on Linux. Of course that made the very low resource bittorrent client much more resource hungry. Now this all changed. (Screenshots inside)

µTorrent is only available as "alpha" release, but as it often is with that program, even pre-releases are very stable. And the usability -- one would not expect much from an alpha release here either -- is excellent. It comes as a tar package with a binary inside called "utorrent-server". Why it's called "server" and not just "utorrent", I don't know. Fact is, though, that you can only control is via the web interface (or the config files).

µTorrent running inside Chrome in Ubuntu 10.04

There won't be a special µTorrent window on your desktop, but rather a tab in your browser. And it looks exactly like the Windows/WINE user interface. You can do everything the way you are used to doing it with utorrent, just inside your browser. Hence configuration is just as easy and comfortable.

It downloads as fast as you're used to from Windows and WINE and uses only about 2.5 MB of memory on my system. The average CPU usage on my celeron with 1.7 Ghz is 10 %. You can set it to automatically download torrent files saved inside a certain directory so you won't ever need to open the UI webpage. But if you do want to open it lots of nice graphs and statistics are waiting for you.

All you need to know to get started is the URL to connect to utorrent, user and password:
Url: http://localhost:8080/gui/
Username: admin
Password: (empty)

So go get it and try it out yourself! (Update: sorry about the broken link!)

I don't know where you got that piece of information from, but uTorrent is written in C++.

"Small executable size is achieved by avoiding the use of many libraries, notably the C++ standard library and stream facilities, and creating substitutes written specifically for the program. The executable is then compressed to roughly half of its compiled and linked size using UPX."